1. Technical Field
The present disclosure relates to a frequency generation device and a method of generating an output frequency using the frequency generation device.
2. Description of the Related Art
An oscillator is an electronic device capable of generating a periodic signal having an oscillation frequency (for example, a sine wave or a square wave).
There are many different types of oscillators, such as ring oscillators, resistance capacitance (RC) oscillators, crystal oscillators, etc.
A ring oscillator may include a circuit having a gate propagation delay time that can be modified to produce a desired oscillation frequency. The gate propagation delay time may be modified, for example, by changing the number of gate circuits in the ring oscillator circuit, or by connecting a capacitor and a resistor between the gate circuits, so as to adjust the oscillation frequency.
Similarly, the oscillation frequency of a resistance capacitance (RC) oscillator can be adjusted by changing the capacitance or resistance value of the gate circuits in the RC-type oscillator.
Ring oscillators and RC oscillators are widely used in electronic devices due to their low cost. However, the frequencies generated by the ring oscillators and the RC oscillators may lack the accuracy required for some applications. For example, the accuracy of a ring oscillator is within ±50% before trimming, and within ±5% after trimming, which may not be accurate enough for certain applications.
A crystal oscillator typically includes a quartz crystal. Due to advances in the crystal cutting process, the crystal oscillator may have a more precise and stable oscillation frequency compared to the ring oscillator or RC oscillator. However, the crystal oscillator is typically more expensive than the ring oscillator and the RC oscillator. As a result, the use of a crystal oscillator may increase device costs.
In some oscillators, the oscillation frequency may be automatically adjusted using digital control. For example, U.S. Patent Application Publication No. 2010/0085121 A1 discloses an auto trimming oscillator including a Successive Approximation Register (SAR) that is used to iteratively trim the oscillator output clock frequency based on a difference between a reference clock frequency and the oscillator output clock frequency. Specifically, the output frequency of a voltage controlled oscillator signal may be adjusted by modifying the oscillation frequency and comparing the modified oscillation frequency with the reference clock frequency.